1. Field of the Invention
The invention is in the field of implantable infusion devices having a plurality of penetrable self-sealing septums leading to a plurality of open cavities which are implanted under the skin of a patient, whereby medications or other fluids may be introduced into the device by means of a hypodermic needle or catheter for dispensing the medications to selected areas of the body.
2. The Related Technology
A variety of implantable infusion devices, also known as implantable ports, are well known in the art. These usually comprise a housing portion which is received on a base portion having an open cavity formed therein which is accessible through a reduced entry passage in the upper end of the housing portion, a penetrable sealed portion which is received in the entry passage in the housing portion, and means for one or more outlets to communicate with the open cavities for dispensing the medication to a predetermined location. The medication is dispensed from the outlets to the predetermined location by the use of a catheter element.
The implantable device is implanted under the skin of a patient, preferably together with a catheter which communicates between the open cavities and some other portion of the body, such as the venous system. The implantable device typically acts as an implantable injection cap for the direct infusion of medication or fluid. Additional quantities of medication or fluid may, thereafter, be dispensed from the open cavity subsequent to an initial injection by means of a hypodermic needle or catheter or cannula which passes through the skin of the patient and the septum into the open cavity.
Medication or fluid may be dispensed or infused to a point of application in a variety of procedures. One procedure for dispensing medication or fluid provides for a bolus infusion. The infusion of a drug by this procedure involves the injection of a drug through an insertion route created by a syringe passing through the septum through the open cavity to the point of application. Thereafter, the insertion route is flushed with saline, heparin or a combination thereof (resulting in a heparin-lock) to cleanse the insertion route and prevent infection or contamination.
Alternatively, one may continually infuse medication or fluid to a point of application. This procedure for dispensing medication or fluid involves the use of a catheter and needle, which is attached to an ambulatory-type pump or an IV bag suspended above a patient, to communicate with the insertion route defined by the implantable infusion device. The ambulatory-type pump, or IV bag, by virtue of gravity, continually feed the medication or fluid through the insertion route to the point of application.
Whereas the infusion of medication or fluid is often practiced, implantable devices may be used to withdraw fluids from a patient, such as blood. This procedure involves the use of a needle communicating with the insertion route (or, in this case, withdrawal route) to draw blood from a point in the body, usually the venous system. Blood initially withdrawn from a patient is discarded due to possible contamination, but subsequent samples are taken for testing or other uses. Thereafter, to prevent clotting, the withdrawal route is flushed as previously described.
Certain basic problems have been experienced with such devices. In order to supply medication to the open cavity, it becomes necessary to locate the septum covering the open cavity. Because the implantable device is subcutaneously placed, this is normally effected by feel. Generally, a septum on an implantable device is smooth and relatively flat and, therefore, due to the subcutaneous placement of the implantable device, most individuals are incapable of identifying the location of the septum tactilely.
Whereas the use of a type of tactile locating device for the septum has been attempted in the art, this tactile locating device has not proven to be particularly useful in the art. This type of tactile locating device involves the placement of a raised circular ring about the entire outer perimeter of a septum. Such a construction has raised concern to some individuals.
Doctors are concerned that necrosis may develop in response to such an enclosed circular ring about the septum. They fear that the enclosed area encircled by the circular ring may result in the blood supply to the enclosed area becoming adversely affected, thus allowing necrosis to develop. This not only adversely affects the localized tissue, but interferes with the infusion or withdrawal of medication or fluid from the implantable infusion device.
Even if an individual could determine the location of the septum by touch, a further problem is presented. That portion of the septum that can be positively identified is usually only the perimeter of the rubberized septum, differentiated at its perimeter by the rigid surrounding housing portion. Most individuals will attempt to access the open cavity at a point next to the septum perimeter to ensure the cavity is accessed and prevent their straying away from the septum area.
The fact that individuals attempt to access the septum at its perimeter is detrimental in that the puncture life of the septum in that area is reduced. Normally, if one could identify the septum in its entirety, one would not concentrate the area susceptive to a needle puncture (at the perimeter) but, instead, one would disseminate punctures about the surface of the septum. The life of the septum lasts as long as any one spot in the septum continues to self-seal after being punctured.
There is a direct correlation between the area of a septum to be punctured, and the puncture life of the entire septum. As the area to be repeatedly punctured increases, it is less likely any one spot will experience the repeated puncturing action, and the life of the septum is prolonged. As the area to be repeatedly punctured decreases, it is more likely that any one spot will experience the repeated puncturing action, and the life of the septum is reduced. Thus, the use of a circular ring about the entire perimeter of the septum, causing individuals to repeatedly puncture a limited area of the septum detrimentally, acts to reduce the life of the septum.
Another reason for the need to be sure a septum is accessed (and, thus, the reason individuals will access a septum at its perimeter) has to do with the types of drugs being injected into the implantable device. Sometimes a vesicant drug (one toxic to cellular structures) is injected into an area of the body. Should the vesicant drug be injected about the outside of the housing of the device, instead of through the insertion route defined by the implantable device, necrosis of tissues about the device may occur. Extravasation about the housing results in instability to the implantable device, and possible harm to a patient. One may improperly believe they have accessed the septum if the base of the implantable device is struck by the accessing needle, thus resulting in the dispensation of the vesicant drug to the tissue about the implantable device.
Another problem presented by the use of a raised circular ring is where two septums covering open cavities are implanted in a side-by-side position, but spaced apart somewhat so that two different types of medication may be utilized. In this situation, the doctor has the problem after locating one of the septums, to determine where the second septum is. If the doctor can identify the perimeter of the first septum, the doctor knows that the second septum is positioned somewhere in a circular path around the first septum. However, it becomes necessary to probe around this circular path in order to locate the position of the second septum by virtue of the second raised circular ring. While one might think that locating the second septum would be relatively easy, doctors have experienced some difficulty in this process, particularly when the implantable device has been in position for a long period of time. While a doctor feels about for the septums, the very process of locating the septums impedes access to the septums since the fingers of the doctor are covering one or both of the septums.
Moreover, even if a doctor should identify the location of the first septum and the second septum, a problem still exists. Typically all septums are constructed in a similar fashion. This similarity prevents a doctor from differentiating one septum from another due to the subcutaneous placement of the implantable device. Because multiple septums are generally employed to act as alternate insertion routes to isolate medication and fluids which react with each other, the problem could occur that reactive substances may be placed through the same septum. The potentially harmful circumstances resulting from such an occurrence can be devastating.
An additional problem arises from the fact that the location of structures, separate from the septums, but important nonetheless, cannot be determined due to the subcutaneous placement of the implantable device. Structures, such as the stem of a port, are vital to the continued functioning of a port. It would be a benefit to know their location as well as that of any septums.
Thus, it has become obvious that needed improvements over the prior art would be very desirable, such as a tactile means that more definitively and simultaneously locates the position of each of a plurality of septums, that does not create an enclosed area, that obviates the restriction of access to the septums by the very process of locating the septum, that maximizes the life-span of the septums, which provides some indicating means for locating the stem of a port, and that differentiates between a plurality of septums such that two or more reactive chemicals do not come in contact with each other in the same port chamber to cause a precipitate which could harm a patient.